For the canning of some edible products, for example oats, it is usual practice for a can manufacturer to supply to the producer of the edible product an open-bottomed can body that has been pre-sealed with a peelable heat sealed membrane lid over the opening at the top end of the can body, along with a separate can bottom or end. The peelable lid is typically formed of a metal foil, and may be embossed with a pattern or a logo in order to give it an aesthetically pleasing appearance to the consumer. The edible product producer fills the can through the bottom opening before closing the can body by seaming the can bottom over the opening. A plastic overcap is often placed over the top end of the can, directly over the peelable lid, in order to protect the lid. The overcap may be fitted after filling, but usually is pre-fitted to the can body by the can manufacturer in order to reduce the assembly steps that must be performed at the filling facility.
The method described above requires the product to be dispensed into the can body with the can body oriented upside down. As such the product falls and presses down onto the foil lid. Some products are filled under considerable force, for example porridge oats, where a compacting ram is used to force the oats into the can body and to remove air trapped within the product. This is known as “force filling”. Force filling directly onto a foil lid can deform the lid, for example forming wrinkles in the foil and damaging any embossed pattern or logo.
It is possible to avoid this problem by providing the can bodies to the filling facility without the foil lids in place, but rather with a pre-seamed bottom. However, this requires that the foil lids be attached at the filling facility and after filling. This is difficult to achieve, not least because it requires the installation of new production equipment at each of the filling facilities (rather than only at a central can production plant).
Moreover, it might not be practical to attach a foil lid after filling if attachment requires access to the can body from both the top and the bottom ends.